20x and 50x shootout - Phono Stylus Images

[ray_parkhurst]

I shot a new stylus of the same type as the worn one shown in images above using all but the B&L 20x BD. I used a smaller step size than I normally do in order to make sure I captured the unworn surface texture as well as possible. Turns out the BD objectives do a better job from illumination perspective at showing the texture. The MMs with ringlights have either too high or too low or too wide an illumination.

My observation is the 40x Nikon ELWD does the best job at showing the rough surface of the new contact. It also gave the best contrast on the worn contact, so most likely I'll be using it for doing the stylus imaging from now on.

Here are the images:

20x MM

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20x Nikon ELWD

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20x Olympus Neo SPlan

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40x Nikon ELWD

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50x MM

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50x Mitutoyo

[Sym P. le]

Here's the seminal report on diamond styli from 1950. I think it answers the major questions:

https://www.aes.org/aeshc/pdf/how.the.a ... stylus.pdf

If I understand this correctly, the recording industry moved to the LP format circa 1948 with soft vinyl and microgoove technology. The article above is from 1950 and tests several stylus materials against the old and new groove specs. For the standard groove, "... The diamond stylus did not show any wear after 1000 plays." (approx. 50 hrs. of play)

For the new microgroove "... The diamond showed no sign of wear after 15 plays. The microgroove diamond was continued in use for a total of 100 plays or 37 hours. A slight flat was noticed on the diamond at the end of 37 hours. Apparently, stylus wear is far more rapid on microgroove than on standard groove records."

Note also that the microgroove stylus is much finer than the standard grove stylus, 1.0 Mils vs. 2.5 Mils, and the pickup weight is 8 grams to 1.25 oz. (or 35.4 grams), the implication being that the acceleration forces are much greater with the new technology (so much so that sapphire and osmium can no longer be considered for use as a stylus).

Do I understand properly that you are photographing the flat that develops on a used stylus?

Edit: I see now that there are different stylus shapes. Still trying to understand the images, i.e. front of stylus, sides, and wear location.

[rjlittlefield]

Every time I look at these images I am intrigued by the bright ring that surrounds much of the contact patch.

Visually that feature suggests a thin raised lip, but (A) I'm having trouble imagining how such a raised lip would form, and (B) the appearance varies significantly from one image to another.

So now I'm thinking that the bright ring is actually a specular reflection of your ringlight, bouncing off convex surfaces immediately surrounding the contact patch.

Is that your interpretation also, or if not then what do you think it is?

I looked for but could not find an SEM image of a used stylus.

But I was intrigued to see the image at https://www.sciencesource.com/archive/I ... 17468.html , which makes quite vivid what sort of paths the stylus is trying to follow.

--Rik

[ray_parkhurst]

...
Do I understand properly that you are photographing the flat that develops on a used stylus?

Edit: I see now that there are different stylus shapes. Still trying to understand the images, i.e. front of stylus, sides, and wear location.

Yes, the first set of images was of a used stylus with 1000hrs of wear. The second set of images was of a similar but new (<10hrs) stylus. This stylus is an "elliptical" shape, which is the most common type.

[Sym P. le]

Ok, if I understand, the images are of the side of the stylus which has an intentional flat on it and is the contact surface on the groove. The flat gets larger as the stylus wears, which is detrimental to the responsiveness of the stylus not to mention potential damage to the groove.

I've taken the liberty to show worn vs. new using the Mitty images.

Edit: Sorry, I was writing as you posted. Is the small flat intentional or does the wear start straight out of the gate?

[ray_parkhurst]

Every time I look at these images I am intrigued by the bright ring that surrounds much of the contact patch.

Visually that feature suggests a thin raised lip, but (A) I'm having trouble imagining how such a raised lip would form, and (B) the appearance varies significantly from one image to another.

So now I'm thinking that the bright ring is actually a specular reflection of your ringlight, bouncing off convex surfaces immediately surrounding the contact patch.

Is that your interpretation also, or if not then what do you think it is?

I looked for but could not find an SEM image of a used stylus.

But I was intrigued to see the image at https://www.sciencesource.com/archive/I ... 17468.html , which makes quite vivid what sort of paths the stylus is trying to follow.

--Rik

Yes, that is what I believe is happening. As I said in the first post, "this creates a dark contact patch surrounded by a bright ring of light where the light reflects directly to the sensor".

I too have searched for SEM images of styli, and have only seen one, but it did not show the wear patches. The image you linked to is pretty good and shows the record groove nicely.

Edited to add: there may additionally be an effect due to the polished diamond surface that causes an increased brightness to the circle surrounding that surface when illuminated with the ringlight.

[ray_parkhurst]

Ok, if I understand, the images are of the side of the stylus which has an intentional flat on it and is the contact surface on the groove. The flat gets larger as the stylus wears, which is detrimental to the responsiveness of the stylus not to mention potential damage to the groove.

I've taken the liberty to show old vs. new using the Mitty images.
...
Edit: Sorry, I was writing as you posted. Is the small flat intentional or does the wear start straight out of the gate?

There is actually no flat on the new stylus. The darker area is due to the reduced reflections from those surfaces, but if you look closely you can see the same rough texture on the diamond surface as on other parts of the stylus. Because of the method I use, the darker patch is the exact area that contacts the record groove.

Edited to add: some more expensive styli are intentionally polished on their contact surfaces, but not to form flats, just to remove the surface roughness.

Edited to add: I recently shot a very interesting stylus shape, the Ortofon "Replicant". Here is one contact patch. This one confuses many folks, even some that are familiar with the shape:
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[Sym P. le]

Thanks for the explains.

Here's a side by side with the 40x Nikon ELWD (9.8mm w.d.) which de-emphasizes the dark patch on the new stylus.

Edit: Is the wear patch center line aft of the stylus center line or forward?

Edit 2: It looks like .....

Edit 3: The resolution/sharpness .....

Edit 4: My bad, while aligning the images, I rotated them and did far more damage than I thought would occur. My apologies. (Please don't throw pennies)

Edit 5: I've replaced the images with non-rotated crops so that the original resolution/sharpness can be seen. It's still interesting that you did better with the used stylus than the new one regardless of the objective. Thanks for you patience.


[/2cents]

[colohank]

Interesting article, but a bit contradictory. If diamond is the hardest substance, and if it takes diamond to cut diamond, then how can particles of dust in a record's grooves abrade a diamond stylus? In fact, they can't. Well, unless they're diamond dust.

[Sym P. le]

Diamond is not cut, it's cleaved. Although it is harder than any other substance, it has comparatively weak cleavage planes. For a phonograph needle that is already oscillating at high frequencies, if it hits a spec of dirt and is also accelerated in a vertical direction, this impact can cleave a chunk off the side. Summary, BAD!

[chris_ma]

you're probably seen this one, but for those who haven't...

Electron microscope slow-motion video of vinyl LP:
https://www.youtube.com/watch?v=GuCdsyCWmt8

around the 4min mark one can see the movement, and around 6min there's closeups of the tip.

[colohank]

I concur with the idea that stylus "wear" is an aggregation, over time, of micro-cleavages caused by innumerable tiny impacts.

[Scarodactyl]

It likely osn't just cleavage. Once a piece has broken off it will also be dragged across the surface and abrade it. This is a familiar problem when faceting some materials as well and can ruin your day.

[ray_parkhurst]

I'm not sure if "micro-cleavages" fully explain what is happening. The contact patches are always in exact alignment with the groove, not with crystal cleavage directions. If a micro-cleavage argument can explain this, then it must be that all crystals "wear" through micro-cleavage.

Some more info may be useful. This stylus was played on one side of one record, on a linear tracking turntable in repeat mode, for 1000 hours. The record was cleaned after each check point. Vertical tracking force was 1.25g. I think this is a near best case scenario, which is why the resulting wear is minimal, but wear flats did indeed form gradually over the playing time. If micro-cleavages are to explain this, then I'm not sure it's possible to separate them from other forms of wear, except that the wear was on a crystalline rather than amorphous substance.

[ray_parkhurst]

Edit 5: I've replaced the images with non-rotated crops so that the original resolution/sharpness can be seen. It's still interesting that you did better with the used stylus than the new one regardless of the objective. Thanks for you patience.

I probably did slightly different processing on the first group vs the second, but for comparison purposes made sure the processing was the same between groups. I think I added a little sharpening to the first group but not to the second.

I also just realized that I shot the Oly 20x using a tube lens in first images, but without the tube lens in second set. So the difference in that objective is infinite vs finite configuration.